3D semiconductor memory device and structure

ABSTRACT

A semiconductor memory, including: a first memory cell including a first transistor; a second memory cell including a second transistor; and a memory peripherals transistor, the memory peripherals transistor is overlaying the second transistor or is underneath the first transistor, where the second memory cell overlays the first memory cell at a distance of less than 200 nm, and where the memory peripherals transistor is part of a peripherals circuit controlling the memory.

CROSS-REFERENCE OF RELATED APPLICATION

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 14/821,683, filed on Aug. 7, 2015, which is acontinuation-in-part of U.S. patent application Ser. No. 13/492,395,(now U.S. Pat. No. 9,136,153 issued on Sep. 15, 2015) filed on Jun. 8,2012, which is a continuation of U.S. patent application Ser. No.13/273,712 (now U.S. Pat. No. 8,273,610 issued on Sep. 25, 2012) filedOct. 14, 2011, which is a continuation-in-part of U.S. patentapplication Ser. No. 13/016,313 (now U.S. Pat. No. 8,362,482 issued onJan. 29, 2013) filed on Jan. 28, 2011, which is a continuation-in-partof U.S. patent application Ser. No. 12/970,602, filed on Dec. 16, 2010,which is a continuation-in-part of U.S. patent application Ser. No.12/949,617, (now U.S. Pat. No. 8,754,533 issued on Jun. 17, 2014) filedon Nov. 18, 2010. The contents of the foregoing applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This application relates to the general field of Integrated Circuit (IC)devices and fabrication methods, and more particularly to multilayer orThree Dimensional Integrated Circuit (3D IC) devices and fabricationmethods.

2. Discussion of Background Art

Semiconductor manufacturing is known to improve device density in anexponential manner over time, but such improvements come with a price.The mask set cost required for each new process technology has also beenincreasing exponentially. While 20 years ago a mask set cost less than$20,000, it is now quite common to be charged more than $1 M for today'sstate of the art device mask set.

These changes represent an increasing challenge primarily to customproducts, which tend to target smaller volume and less diverse marketstherefore making the increased cost of product development very hard toaccommodate.

Custom Integrated Circuits can be segmented into two groups. The firstgroup includes devices that have all their layers custom made. Thesecond group includes devices that have at least some generic layersused across different custom products. Well-known examples of the secondkind may include Gate Arrays, which use generic layers for all layers upto a contact layer that couples the silicon devices to the metalconductors, and Field Programmable Gate Array (FPGA) devices where allthe layers are generic. The generic layers in such devices may mostly bea repeating pattern structure, called a Master Slice, in an array form.

The logic array technology may be based on a generic fabric customizedfor a specific design during the customization stage. For an FPGA thecustomization may be done through programming by electrical signals. ForGate Arrays, which in their modern form are sometimes called StructuredApplication Specific Integrated Circuits (or Structured ASICs), thecustomization may be by at least one custom layer, which might be donewith Direct Write eBeam or with a custom mask. As designs tend to behighly variable in the amount of logic and memory and type of input &output (I/O) each one may need, vendors of logic arrays create productfamilies, each product having a different number of Master Slicescovering a range of logic, memory size and I/O options. Yet, it istypically a challenge to come up with minimum set of Master Slices thatcan provide a good fit for the maximal number of designs because it maybe quite costly to use a dedicated mask set for each product.

U.S. Pat. No. 4,733,288 issued to Sato in March 1988 (“Sato”), disclosesa method “to provide a gate-array LSI chip which can be cut into aplurality of chips, each of the chips having a desired size and adesired number of gates in accordance with a circuit design.” Thereferences cited in Sato present a few alternative methods to utilize ageneric structure for different sizes of custom devices.

The array structure may fit the objective of variable sizing. Thedifficulty to provide variable-sized array structure devices may resultfrom the need of providing I/O cells and associated pads to connect thedevice to the package. To overcome this difficulty Sato suggests amethod wherein I/O could be constructed from the transistors also usedfor the general logic gates. Anderson also suggested a similar approach.U.S. Pat. No. 5,217,916 issued to Anderson et al. on Jun. 8, 1993,discloses a borderless configurable gate array free of predefinedboundaries using transistor gate cells, of the same type of cells usedfor logic, to serve the input and output function. Accordingly, theinput and output functions may be placed to surround the logic arraysized for the specific application. This method may place a potentiallimitation on the I/O cell to use the same type of transistors as usedfor the logic and; hence, may not allow the use of higher operatingvoltages for the I/O.

U.S. Pat. No. 7,105,871 issued to Or-Bach et al. on Sep. 12, 2006,discloses a semiconductor device that includes a borderless logic arrayand area I/Os. The logic array may comprise a repeating core, and atleast one of the area I/Os may be a configurable I/O.

In the past it was reasonable to design an I/O cell that could beconfigured to the various needs of most customers. The ever increasingneed of higher data transfer rate in and out of the device drove thedevelopment of special serial I/O circuits called SerDes(Serializer/Deserializer) transceivers. These circuits are complex andmay lead to a far larger silicon area than conventional I/Os.Consequently, the variations may be combinations of various amounts oflogic, various amounts and types of memories, and various amounts andtypes of I/O. This implies that even the use of the borderless logicarray of the prior art may still lead to multiple expensive mask sets.

There are many techniques to construct 3D stacked integrated circuits orchips including:

Through-silicon via (TSV) technology: Multiple layers of transistors(with or without wiring levels) can be constructed separately. Followingthis, they can be bonded to each other and connected to each other withthrough-silicon vias (TSVs).

Monolithic 3D technology: With this approach, multiple layers oftransistors and wires can be monolithically constructed. Some monolithic3D approaches are described in U.S. Pat. Nos. 8,273,610, 8,557,632,8,298,875, 8,642,416, 8,362,482, 8,378,715, 8,379,458, 8,450,804,8,574,929, 8,581,349, 8,642,416, 8,687,399, 8,742,476, 8,754,533,8,674,470, 8,803,206, 8,902,663, 8,994,404, 9,021,414, 9,023,688,9,030,858, 9,117,749, 9,136,153, 9,219,005; U.S. patent publication2011/0092030, 2016/0218046; and U.S. Patent Applications, 62/077,280,62/042,229, 61/932,617, 14/607,077, 14/642,724, 62/139,636, 62/149,651,62/198,126, 62/239,931, 62/246,054, 62/307,568, 62/297,857, Ser. Nos.15/095,187, 15/150,395, 15/173,686, 62/383,463, 15/243,941,PCT/US16/52726, 62/406,376, 62/432,575, 62/440,720, 62/297,857,62/443,751, Ser. Nos. 15/333,138, 15/344,562, and 15/351,389. The entirecontents of the foregoing patents, publications, and applications areincorporated herein by reference.

Electro-Optics: There is also work done for integrated monolithic 3Dincluding layers of different crystals, such as U.S. Pat. Nos.8,283,215, 8,163,581, 8,753,913, 8,823,122, 9,197,804; and U.S. patentapplication Ser. No. 14/461,539. The entire contents of the foregoingpatents, publications, and applications are incorporated herein byreference.

Additionally the 3D technology according to some embodiments of theinvention may enable some very innovative IC alternatives with reduceddevelopment costs, increased yield, and other illustrative benefits.

SUMMARY

The invention may be directed to multilayer or Three DimensionalIntegrated Circuit (3D IC) devices and fabrication methods.

In one aspect, a semiconductor memory, comprising: a first memory cellcomprising a first transistor; a second memory cell comprising a secondtransistor; and a memory peripherals transistor, said memory peripheralstransistor is overlaying said second transistor or is underneath saidfirst transistor, wherein said second memory cell overlays said firstmemory cell at a distance of less than 200 nm, and wherein said memoryperipherals transistor is part of a peripherals circuit controlling saidmemory.

In another aspect, A semiconductor memory, comprising: a first memorycell comprising a first transistor; a second memory cell comprising asecond transistor; and a memory peripherals transistor, said memoryperipherals transistor is overlaying said second transistor or isunderneath said first transistor, wherein said second memory celloverlays said first memory cell at a distance of less than 200 nm, andwherein the misalignment between said first transistor and said memoryperipherals transistor is less than 40 nm.

In another aspect, A semiconductor memory, comprising: a first memorycell comprising a first transistor; a second memory cell comprising asecond transistor; and a memory peripherals transistor, said memoryperipherals transistor is overlaying said second transistor or isunderneath said first transistor, wherein said second memory celloverlays said first memory cell at a distance of less than 200 nm, andwherein said memory peripherals transistor comprises a single crystalchannel and is part of a peripherals circuit controlling said memory.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will be understood and appreciatedmore fully from the following detailed description, taken in conjunctionwith the drawings in which:

FIG. 1 is an exemplary drawing illustration of a programmable devicelayers structure;

FIG. 1A is an exemplary drawing illustration of a programmable devicelayers structure;

FIGS. 1B-1I are exemplary drawing illustrations of the preprocessedwafers and layers and generalized layer transfer;

FIG. 2 is an exemplary drawing illustration of a layer transfer processflow;

FIGS. 3A-3J, 3J1, 3J2, 3K are exemplary drawing illustrations of theformation of a resistive memory transistor;

FIGS. 4A-4G are exemplary drawing illustrations of the formation of acharge trap memory transistor;

FIGS. 5A-5J, 5J1, 5J2, 5K are exemplary drawing illustrations of theformation of a resistive memory transistor; and

FIGS. 6A-6J are exemplary drawing illustrations of the formation of aresistive memory transistor with periphery on top.

DETAILED DESCRIPTION

Embodiments of the invention are described herein with reference to thedrawing figures. Persons of ordinary skill in the art will appreciatethat the description and figures illustrate rather than limit theinvention and that in general the figures are not drawn to scale forclarity of presentation. Such skilled persons will also realize thatmany more embodiments are possible by applying the inventive principlescontained herein and that such embodiments fall within the scope of theinvention which is not to be limited except by the appended claims.

Some drawing figures may describe process flows for building devices.These process flows, which may be a sequence of steps for building adevice, may have many structures, numerals and labels that may be commonbetween two or more adjacent steps. In such cases, some labels, numeralsand structures used for a certain step's figure may have been describedin the previous steps' figures.

Some embodiments of the invention may provide a new method forsemiconductor device fabrication that may be highly desirable for customproducts. Some embodiments of the invention may suggest the use of are-programmable antifuse in conjunction with ‘Through Silicon Via’ toconstruct a new type of configurable logic, or as usually called, FPGAdevices. Some embodiments of the invention may provide a solution to thechallenge of high mask-set cost and low flexibility that exists in thecurrent common methods of semiconductor fabrication. An additionalillustrated advantage of some embodiments of the present invention maybe that it could reduce the high cost of manufacturing the manydifferent mask sets needed in order to provide a commercially viablelogic family with a range of products each with a different set ofmaster slices. Some embodiments of the invention may improve upon theprior art in many respects, including, for example, the structuring ofthe semiconductor device and methods related to the fabrication ofsemiconductor devices.

Some embodiments of the invention may reflect the motivation to save onthe cost of masks with respect to the investment that would otherwisehave been necessary to put in place a commercially viable set of masterslices. Some embodiments of the invention may also provide the abilityto incorporate various types of memory blocks in the configurabledevice. Some embodiments of the invention may provide a method toconstruct a configurable device with the desired amount of logic,memory, I/Os, and analog functions.

In addition, some embodiments of the invention may allow the use ofrepeating logic tiles that provide a continuous terrain of logic. Someembodiments of the invention may use a modular approach to constructvarious configurable systems with Through-Silicon-Via (TSV). Once astandard size and location of TSV has been defined one could buildvarious configurable logic dies, configurable memory dies, configurableI/O dies and configurable analog dies which could be connected togetherto construct various configurable systems. In fact, these embodiments ofthe invention may allow mixing and matching among configurable dies,fixed function dies, and dies manufactured in different processes.

Some embodiments of the invention may provide additional illustratedbenefits by making use of special type of transistors placed above orbelow the antifuse configurable interconnect circuits to allow for a farbetter use of the silicon area. In general an FPGA device that utilizesantifuses to configure the device function may include the electroniccircuits to program the antifuses. The programming circuits may be usedprimarily to configure the device and may be mostly an overhead once thedevice is configured. The programming voltage used to program theantifuse may typically be significantly higher than the voltage used forthe operating circuits of the device. The design of the antifusestructure may be designed such that an unused antifuse may notaccidentally get fused. Accordingly, the incorporation of the antifuseprogramming in the silicon substrate may entail special attention for aresulting higher voltage, and additional silicon area may, accordingly,be allocated.

Unlike the operating transistors designed to operate as fast as possibleand to enable fast system performance, the programming circuits couldoperate relatively slowly. Accordingly using a thin film transistor forthe programming circuits could fit very well with the function and mayreduce the needed silicon area.

The programming circuits may, therefore, be constructed with thin filmtransistors, which may be fabricated after the fabrication of theoperating circuitry, on top of the configurable interconnection layersthat incorporate and use the antifuses. An additional illustratedadvantage of such embodiments of the invention may be the ability toreduce cost of the high volume production. One may only need to usemask-defined links instead of the antifuses and their programmingcircuits. One custom via mask may be used, and this may save stepsassociated with the fabrication of the antifuse layers, the thin filmtransistors, and/or the associated connection layers of the programmingcircuitry.

In accordance with an embodiment of the invention an Integrated Circuitdevice may thus be provided, including a plurality of antifuseconfigurable interconnect circuits and a plurality of transistors toconfigure at least one of said antifuses; wherein said transistors arefabricated after said antifuse.

Further provided in accordance with an embodiment of the invention mayprovide an Integrated Circuit device including: a plurality of antifuseconfigurable interconnect circuits and plurality of transistors toconfigure at least one of said antifuses; wherein said transistors areplaced over said antifuse.

Still further in accordance with an embodiment of the illustratedinvention of the Integrated Circuit device may include second antifuseconfigurable logic cells and a plurality of second transistors toconfigure said second antifuses wherein these second transistors may befabricated before said second antifuses.

Still further in accordance with an embodiment of the illustratedinvention the Integrated Circuit device may also include second antifuseconfigurable logic cells and a plurality of second transistors toconfigure said second antifuses wherein said second transistors may beplaced underneath said second antifuses.

Further provided in accordance with an embodiment of the illustratedinvention may be an Integrated Circuit device including: first antifuselayer, at least two metal layers over it and a second antifuse layeroverlaying the two metal layers.

In accordance with an embodiment of the invention a configurable logicdevice may be presented, including: antifuse configurable look up tablelogic interconnected by antifuse configurable interconnect.

In accordance with an embodiment of the illustrated invention aconfigurable logic device may also be provided, including: a pluralityof configurable look up table logic, a plurality of configurableprogrammable logic array (PLA) logic, and a plurality of antifuseconfigurable interconnect.

In accordance with an embodiment of the invention a configurable logicdevice may also be provided, including: a plurality of configurable lookup table logic and a plurality of configurable drive cells wherein thedrive cells may be configured by plurality of antifuses.

In accordance with an embodiment of the illustrated invention, aconfigurable logic device may additionally be provided, including:configurable logic cells interconnected by a plurality of antifuseconfigurable interconnect circuits wherein at least one of the antifuseconfigurable interconnect circuits may be configured as part of a nonvolatile memory.

Further in accordance with an embodiment of the invention, theconfigurable logic device may include at least one antifuse configurableinterconnect circuit, which may also be configurable to a PLA function.

In accordance with an alternative embodiment of the invention, anintegrated circuit system may also be provided, including a configurablelogic die and an I/O die wherein the configurable logic die may beconnected to the I/O die by the use of Through-Silicon-Via.

Further in accordance with an embodiment of the invention, theintegrated circuit system may include; a configurable logic die and amemory die wherein the configurable logic die and the memory die may beconnected by the use of Through-Silicon-Via.

Still further in accordance with an embodiment of the invention theintegrated circuit system may include a first configurable logic die andsecond configurable logic die wherein the first configurable logic dieand the second configurable logic die may be connected by the use ofThrough-Silicon-Via.

Moreover in accordance with an embodiment of the invention, theintegrated circuit system may include an I/O die that may be fabricatedutilizing a different process than the process utilized to fabricate theconfigurable logic die.

Further in accordance with an embodiment of the invention, theintegrated circuit system may include at least two logic dies connectedby the use of Through-Silicon-Via and wherein some of theThrough-Silicon-Vias may be utilized to carry the system bus signal.

Moreover in accordance with an embodiment of the invention, theintegrated circuit system may include at least one configurable logicdevice.

Further in accordance with an embodiment of the invention, theintegrated circuit system may include, an antifuse configurable logicdie and programmer die which may be connected by the use ofThrough-Silicon-Via.

Additionally there is a growing need to reduce the impact of inter-chipinterconnects. In fact, interconnects may be now dominating ICperformance and power. One solution to shorten interconnect may be touse a 3D IC. Currently, the only known way for general logic 3D IC is tointegrate finished device one on top of the other by utilizingThrough-Silicon-Vias as now called TSVs. The problem with TSVs may bethat their large size, usually a few microns each, may severely limitthe number of connections that can be made. Some embodiments of theinvention may provide multiple alternatives to constructing a 3D ICwherein many connections may be made less than one micron in size, thusenabling the use of 3D IC technology for most device applications.

Additionally some embodiments of the invention may offer new devicealternatives by utilizing the proposed 3D IC technology.

Unlike prior art, various embodiments of the present invention suggestconstructing the programming transistors not in the base silicondiffusion layer but rather above or below the antifuse configurableinterconnect circuits. The programming voltage used to program theantifuse may be typically significantly higher than the voltage used forthe operational circuits of the device. This may be part of the designof the antifuse structure so that the antifuse may not becomeaccidentally activated. In addition, extra attention, design effort, andsilicon resources might be needed to make sure that the programmingphase may not damage the operating circuits. Accordingly theincorporation of the antifuse programming transistors in the siliconsubstrate may need attention and extra silicon area.

Unlike the operational transistors designed to operate as fast aspossible and so to enable fast system performance, the programmingcircuits could operate relatively slowly. Accordingly, a thin filmtransistor for the programming circuits could provide the function andcould reduce the silicon area.

Alternatively other type of transistors, such as Vacuum FET, bipolar,etc., could be used for the programming circuits and may be placed notin the base silicon but rather above or below the antifuse configurableinterconnect.

Yet in another alternative the programming transistors and theprogramming circuits could be fabricated on SOI wafers which may then bebonded to the configurable logic wafer and connected to it by the use ofthrough-silicon-via (TSV), or through layer via (TLV). An illustratedadvantage of using an SOI wafer for the antifuse programming functionmay be that the high voltage transistors that could be built on it arevery efficient and could be used for the programming circuitry includingsupport functions such as the programming controller function. Yet as anadditional variation, the programming circuits could be fabricated by anolder process on SOI wafers to further reduce cost. Moreover, theprogramming circuits could be fabricated by a different processtechnology than the logic wafer process technology. Furthermore, thewafer fab that the programing circuits may be fabricated at may bedifferent than the wafer fab that the logic circuits are fabricated atand located anywhere in the world.

A common objective may be to reduce cost for high volume productionwithout redesign and with minimal additional mask cost. The use ofthin-film-transistors, for the programming transistors, may enable arelatively simple and direct volume cost reduction. Instead of embeddingantifuses in the isolation layer a custom mask could be used to definevias on substantially all the locations that used to have theirrespective antifuse activated. Accordingly the same connection betweenthe strips that used to be programmed may now be connected by fixedvias. This may allow saving the cost associated with the fabrication ofthe antifuse programming layers and their programming circuits. Itshould be noted that there might be differences between the antifuseresistance and the mask defined via resistance. A conventional way tohandle it may be by providing the simulation models for both options sothe designer could validate that the design may work properly in bothcases.

An additional objective for having the programming circuits above theantifuse layer may be to achieve better circuit density. Manyconnections may be needed to connect the programming transistors totheir respective metal strips. If those connections are going upwardthey could reduce the circuit overhead by not blocking interconnectionroutes on the connection layers underneath.

FIG. 1 is a drawing illustration of a programmable device layersstructure according to an alternative embodiment of the invention. Inthis alternative embodiment, there are two layers including antifuses.The first may be designated to configure the logic terrain and, in somecases, may also configure the logic clock distribution. The firstantifuse layer could also be used to manage some of the powerdistribution to save power by not providing power to unused circuits.This layer could also be used to connect some of the long routing tracksand/or connections to the inputs and outputs of the logic cells.

The device fabrication of the example shown in FIG. 1 may start with thesemiconductor substrate, such as monocrystalline silicon substrate 102,comprising the transistors used for the logic cells and also the firstantifuse layer programming transistors. Thereafter, logic fabric/firstantifuse layer 104 may be constructed, which may include multiplelayers, such as Metal 1, dielectric, Metal 2, and sometimes Metal 3.These layers may be used to construct the logic cells and often I/O andother analog cells. In this alternative embodiment of the invention, aplurality of first antifuses may be incorporated in the isolation layerbetween metal 1 and metal 2 or in the isolation layer between metal 2and metal 3 and the corresponding programming transistors could beembedded in the silicon substrate 102 being underneath the firstantifuses. The first antifuses could be used to program logic cells andto connect individual cells to construct larger logic functions. Thefirst antifuses could also be used to configure the logic clockdistribution. The first antifuse layer could also be used to manage someof the power distribution to save power by not providing power to unusedcircuits. This layer could also be used to connect some of the longrouting tracks and/or one or more connections to the inputs and outputsof the cells.

Interconnection layer 106 could include multiple layers of longinterconnection tracks for power distribution and clock networks, or aportion thereof, in addition to structures already fabricated in thefirst few layers, for example, logic fabric/first antifuse layer 104.

Second antifuse layer 107 could include many layers, including theantifuse configurable interconnection fabric. It might be called theshort interconnection fabric, too. If metal 6 and metal 7 are used forthe strips of this configurable interconnection fabric then the secondantifuse may be embedded in the dielectric layer between metal 6 andmetal 7.

The programming transistors and the other parts of the programmingcircuit could be fabricated afterward and be on top of the configurableinterconnection fabric programming transistors 110. The programmingelement could be a thin film transistor or other alternatives for overoxide transistors as was mentioned previously. In such case the antifuseprogramming transistors may be placed over the antifuse layer, which maythereby enable the configurable interconnect in second antifuse layer107 or logic fabric/first antifuse layer 104. It should be noted that insome cases it might be useful to construct part of the control logic forthe second antifuse programming circuits, in the base layers such assilicon substrate 102 and logic fabric/first antifuse layer 104.

The final step may include constructing the connection to the outside112. The connection could be pads for wire bonding, soldering balls forflip chip, optical, or other connection structures such as thoseconnection structures for TSV.

In another alternative embodiment of the invention the antifuseprogrammable interconnect structure could be designed for multiple use.The same structure could be used as a part of the interconnectionfabric, or as a part of the PLA logic cell, or as part of a Read OnlyMemory (ROM) function. In an FPGA product it might be desirable to havean element that could be used for multiple purposes. Having resourcesthat could be used for multiple functions could increase the utility ofthe FPGA device.

FIG. 1A is a drawing illustration of a programmable device layersstructure according to another alternative embodiment of the invention.In this alternative embodiment, there may be an additional circuit ofFoundation layer 114 connected by through silicon via connections 116 tothe fabric/first antifuse layer 104 logic or antifuses. This underlyingdevice of circuit of Foundation layer 114 may provide the programmingtransistor for the logic fabric/first antifuse layer 104. In this way,the programmable device substrate diffusion, such as primary siliconlayer 102A, may not be prone to the cost penalty of the programmingtransistors for the logic fabric/first antifuse layer 104. Accordinglythe programming connection of the logic fabric/first antifuse layer 104may be directed downward to connect to the underlying programming deviceof Foundation layer 114 while the programming connection to the secondantifuse layer 107 may be directed upward to connect to the programmingcircuit programming transistors 110. This could provide less congestionof the circuit internal interconnection routes.

FIG. 1A is a cut illustration of a programmable device, with twoantifuse layers. The programming transistors for the first logicfabric/first antifuse layer 104 could be prefabricated on Foundationlayer 114, and then, utilizing “smart-cut”, a single crystal, ormono-crystalline, transferred silicon layer 204 may be transferred onwhich the primary programmable logic of primary silicon layer 102A maybe fabricated with advanced logic transistors and other circuits. Thenmulti-metal layers are fabricated including a lower layer of antifusesin logic fabric/first antifuse layer 104, interconnection layer 106 andsecond antifuse layer 107 with its configurable interconnects. For thesecond antifuse layer 107 the programming transistors 110 could befabricated also utilizing a second “smart-cut” layer transfer.

The term layer transfer in the use herein may be defined as thetechnological process or method that enables the transfer of very finelayers of crystalline material onto a mechanical support, wherein themechanical support may be another layer or substrate of crystallinematerial. For example, the “SmartCut” process, also used herein as theterm ‘ion-cut’ process, together with wafer bonding technology, mayenable a “Layer Transfer” whereby a thin layer of a single ormono-crystalline silicon wafer may be transferred from one wafer orsubstrate to another wafer or substrate. Other specific layer transferprocesses may be described or referenced herein.

The terms monocrystalline or mono-crystalline in the use herein of, forexample, monocrystalline or mono-crystalline layer, material, orsilicon, may be defined as “a single crystal body of crystallinematerial that contains no large-angle boundaries or twin boundaries asin ASTM F1241, also called monocrystal” and “an arrangement of atoms ina solid that has perfect periodicity (that is, no defects)” as in theSEMATECH dictionary. The terms single crystal and monocrystal areequivalent in the SEMATECH dictionary. The term single crystal in theuse herein of, for example, single crystal silicon layer, single crystallayer, may be equivalently defined as monocrystalline.

The term via in the use herein may be defined as “an opening in thedielectric layer(s) through which a riser passes, or in which the wallsare made conductive; an area that provides an electrical pathway[connection path] from one metal layer to the metal layer above orbelow,” as in the SEMATECH dictionary. The term through silicon via(TSV) in the use herein may be defined as an opening in a siliconlayer(s) through which an electrically conductive riser passes, and inwhich the walls are made isolative from the silicon layer; a riser thatprovides an electrical pathway [connection path] from one metal layer tothe metal layer above or below. The term through layer via (TLV) in theuse herein may be defined as an opening in a layer transferred layer(s)through which an electrically conductive riser passes, wherein the risermay pass through at least one isolating region, for example, a shallowtrench isolation (STI) region in the transferred layer, may typicallyhave a riser diameter of less than 200 nm, a riser that provides anelectrical pathway [connection path] from one metal layer to the metallayer above or below. In some cases, a TLV may additionally pass thru anelectrically conductive layer, and the walls may be made isolative fromthe conductive layer.

The reference 108 in subsequent figures can be any one of a vast numberof combinations of possible preprocessed wafers or layers containingmany combinations of transfer layers that fall within the scope of theinvention. The term “preprocessed wafer or layer” may be generic andreference number 108 when used in a drawing figure to illustrate anembodiment of the present invention may represent many differentpreprocessed wafer or layer types including but not limited tounderlying prefabricated layers, a lower layer interconnect wiring, abase layer, a substrate layer, a processed house wafer, an acceptorwafer, a logic house wafer, an acceptor wafer house, an acceptorsubstrate, target wafer, preprocessed circuitry, a preprocessedcircuitry acceptor wafer, a base wafer layer, a lower layer, anunderlying main wafer, a foundation layer, an attic layer, or a housewafer.

FIG. 1B is a drawing illustration of a generalized preprocessed wafer orlayer 108. The wafer or layer 108 may have preprocessed circuitry, suchas, for example, logic circuitry, microprocessors, MEMS, circuitrycomprising transistors of various types, and other types of digital oranalog circuitry including, but not limited to, the various embodimentsdescribed herein. Preprocessed wafer or layer 108 may have preprocessedmetal interconnects and may include copper or aluminum. The metal layeror layers of interconnect may be constructed of lower (less than about400° C.) thermal damage resistant metals such as, for example, copper oraluminum, or may be constructed with refractory metals such as tungstento provide high temperature utility at greater than about 400° C. Thepreprocessed metal interconnects may be designed and prepared for layertransfer and electrical coupling from preprocessed wafer or layer 108 tothe layer or layers to be transferred.

FIG. 1C is a drawing illustration of a generalized transfer layer 109prior to being attached to preprocessed wafer or layer 108. Transferlayer 109 may be attached to a carrier wafer or substrate during layertransfer. Preprocessed wafer or layer 108 may be called a target wafer,acceptor substrate, or acceptor wafer. The acceptor wafer may haveacceptor wafer metal connect pads or strips designed and prepared forelectrical coupling to transfer layer 109. Transfer layer 109 may beattached to a carrier wafer or substrate during layer transfer. Transferlayer 109 may have metal interconnects designed and prepared for layertransfer and electrical coupling to preprocessed wafer or layer 108. Themetal interconnects now on transfer layer 109 may include copper oraluminum. Electrical coupling from transferred layer 109 to preprocessedwafer or layer 108 may utilize through layer vias (TLVs) as theconnection path. Transfer layer 109 may be comprised of single crystalsilicon, or mono-crystalline silicon, or doped mono-crystalline layer orlayers, or other semiconductor, metal, and insulator materials, layers;or multiple regions of single crystal silicon, or mono-crystallinesilicon, or doped mono-crystalline silicon, or other semiconductor,metal, or insulator materials.

FIG. 1D is a drawing illustration of a preprocessed wafer or layer 108Acreated by the layer transfer of transfer layer 109 on top ofpreprocessed wafer or layer 108. The top of preprocessed wafer or layer108A may be further processed with metal interconnects designed andprepared for layer transfer and electrical coupling from preprocessedwafer or layer 108A to the next layer or layers to be transferred.

FIG. 1E is a drawing illustration of a generalized transfer layer 109Aprior to being attached to preprocessed wafer or layer 108A. Transferlayer 109A may be attached to a carrier wafer or substrate during layertransfer. Transfer layer 109A may have metal interconnects designed andprepared for layer transfer and electrical coupling to preprocessedwafer or layer 108A.

FIG. 1F is a drawing illustration of a preprocessed wafer or layer 108Bcreated by the layer transfer of transfer layer 109A on top ofpreprocessed wafer or layer 108A. The top of preprocessed wafer or layer108B may be further processed with metal interconnects designed andprepared for layer transfer and electrical coupling from preprocessedwafer or layer 108B to the next layer or layers to be transferred.

FIG. 1G is a drawing illustration of a generalized transfer layer 109Bprior to being attached to preprocessed wafer or layer 108B. Transferlayer 109B may be attached to a carrier wafer or substrate during layertransfer. Transfer layer 109B may have metal interconnects designed andprepared for layer transfer and electrical coupling to preprocessedwafer or layer 108B.

FIG. 1H is a drawing illustration of preprocessed wafer or layer 108Ccreated by the layer transfer of transfer layer 109B on top ofpreprocessed wafer or layer 108B. The top of preprocessed wafer or layer108C may be further processed with metal interconnect designed andprepared for layer transfer and electrical coupling from preprocessedwafer or layer 108C to the next layer or layers to be transferred.

FIG. 1I is a drawing illustration of preprocessed wafer or layer 108C, a3D IC stack, which may comprise transferred layers 109A and 109B on topof the original preprocessed wafer or layer 108. Transferred layers 109Aand 109B and the original preprocessed wafer or layer 108 may includetransistors of one or more types in one or more layers, metallizationsuch as, for example, copper or aluminum in one or more layers,interconnections to and between layers above and below, andinterconnections within the layer. The transistors may be of varioustypes that may be different from layer to layer or within the samelayer. The transistors may be in various organized patterns. Thetransistors may be in various pattern repeats or bands. The transistorsmay be in multiple layers involved in the transfer layer. Thetransistors may be junction-less transistors or recessed channel arraytransistors. Transferred layers 109A and 109B and the originalpreprocessed wafer or layer 108 may further comprise semiconductordevices such as resistors and capacitors and inductors, one or moreprogrammable interconnects, memory structures and devices, sensors,radio frequency devices, or optical interconnect with associatedtransceivers. Transferred layers 109A and 109B and the originalpreprocessed wafer or layer 108 may further include isolation layers,such as, for example, silicon and/or carbon containing oxides and/orlow-k dielectrics and/or polymers, which may facilitate oxide to oxidewafer or substrate bonding and may electrically isolate, for example,one layer, such as transferred layer 109A, from another layer, such aspreprocessed wafer or layer 108. The terms carrier wafer or carriersubstrate may also be called holder wafer or holder substrate. The termscarrier wafer or substrate used herein may be a wafer, for example, amonocrystalline silicon wafer, or a substrate, for example, a glasssubstrate, used to hold, flip, or move, for example, other wafers,layers, or substrates, for further processing. The attachment of thecarrier wafer or substrate to the carried wafer, layer, or substrate maybe permanent or temporary.

This layer transfer process can be repeated many times, thereby creatingpreprocessed wafers comprising many different transferred layers which,when combined, can then become preprocessed wafers or layers for futuretransfers. This layer transfer process may be sufficiently flexible thatpreprocessed wafers and transfer layers, if properly prepared, can beflipped over and processed on either side with further transfers ineither direction as a matter of design choice.

The thinner the transferred layer, the smaller the through layer via(TLV) diameter obtainable, due to the potential limitations ofmanufacturable via aspect ratios. Thus, the transferred layer may be,for example, less than about 2 microns thick, less than about 1 micronthick, less than about 0.4 microns thick, less than about 200 nm thick,or less than about 100 nm thick. The TLV diameter may be less than about400 nm, less than about 200 nm, less than about 80 nm, less than about40 nm, or less than about 20 nm. The thickness of the layer or layerstransferred according to some embodiments of the present invention maybe designed as such to match and enable the best obtainable lithographicresolution capability of the manufacturing process employed to createthe through layer vias or any other structures on the transferred layeror layers.

In many of the embodiments of the invention, the layer or layerstransferred may be of a crystalline material, for example,mono-crystalline silicon, and after layer transfer, further processing,such as, for example, plasma/RIE or wet etching, may be done on thelayer or layers that may create islands or mesas of the transferredlayer or layers of crystalline material, for example, mono-crystallinesilicon, the crystal orientation of which has not changed Thus, amono-crystalline layer or layers of a certain specific crystalorientation may be layer transferred and then processed whereby theresultant islands or mesas of mono-crystalline silicon have the samecrystal specific orientation as the layer or layers before theprocessing. After this processing, the resultant islands or mesas ofcrystalline material, for example, mono-crystalline silicon, may bestill referred to herein as a layer, for example, mono-crystallinelayer, layer of mono-crystalline silicon, and so on.

Persons of ordinary skill in the art will appreciate that theillustrations in FIGS. 1 through 1I are exemplary only and are not drawnto scale. Such skilled persons will further appreciate that manyvariations may be possible such as, for example, the preprocessed waferor layer 108 may act as a base or substrate layer in a wafer transferflow, or as a preprocessed or partially preprocessed circuitry acceptorwafer in a wafer transfer process flow. Moreover, layer transfertechniques, such as ‘ion-cut’ that may form a layer transfer demarcationplane by ion implantation of hydrogen molecules or atoms, or any otherlayer transfer technique described herein or utilized in industry, maybe utilized in the generalized FIG. 1 flows and applied throughoutherein. Furthermore, metal interconnect strips may be formed on theacceptor wafer and/or transferred layer to assist the electricalcoupling of circuitry between the two layers, and may utilize TLVs. Manyother modifications within the scope of the illustrated embodiments ofthe invention described herein will suggest themselves to such skilledpersons after reading this specification. Thus the invention is to belimited only by the appended claims.

A technology for such underlying circuitry may be to use the “SmartCut”process. The “SmartCut” process is a well understood technology used forfabrication of SOI wafers. The “SmartCut” process, together with waferbonding technology, may enable a “Layer Transfer” whereby a thin layerof a single or mono-crystalline silicon wafer may be transferred fromone wafer to another wafer. The “Layer Transfer” could be done at lessthan about 400° C. and the resultant transferred layer could be evenless than about 100 nm thick. The transferred layer thickness maytypically be about 100 nm, and may be a thin as about 5 nm in currentlydemonstrated fully depleted SOI (FDSOI) wafer manufacturing by Soitec.In most applications described herein in this invention the transferredlayer thickness may be less than about 400 nm and may be less than about200 nm for logic applications. The process with some variations andunder different names may be commercially available by two companies,namely, Soitec (Crolles, France) and SiGen—Silicon Genesis Corporation(San Jose, Calif.). A room temperature wafer bonding process utilizingion-beam preparation of the wafer surfaces in a vacuum has been recentlydemonstrated by Mitsubishi Heavy Industries Ltd., Tokyo, Japan. Thisprocess may allow for room temperature layer transfer.

Alternatively, other technology may also be used. For example, othertechnologies may be utilized for layer transfer as described in, forexample, IBM's layer transfer method shown at IEDM 2005 by A. W. Topol,et. al. The IBM's layer transfer method employs a SOI technology andutilizes glass handle wafers. The donor circuit may be high-temperatureprocessed on an SOI wafer, temporarily bonded to a borosilicate glasshandle wafer, backside thinned by chemical mechanical polishing of thesilicon and then the Buried Oxide (BOX) is selectively etched off. Thenow thinned donor wafer may be subsequently aligned and low-temperatureoxide-to-oxide bonded to the acceptor wafer topside. A low temperaturerelease of the glass handle wafer from the thinned donor wafer may beperformed, and then through bond via connections may be made.Additionally, epitaxial liftoff (ELO) technology as shown by P.Demeester, et. al, of IMEC in Semiconductor Science Technology 1993 maybe utilized for layer transfer. ELO may make use of the selectiveremoval of a very thin sacrificial layer between the substrate and thelayer structure to be transferred. The to-be-transferred layer of GaAsor silicon may be adhesively ‘rolled’ up on a cylinder or removed fromthe substrate by utilizing a flexible carrier, such as, for example,black wax, to bow up the to-be-transferred layer structure when theselective etch, such as, for example, diluted Hydrofluoric (HF) Acid,may etch the exposed release layer, such as, for example, silicon oxidein SOI or AlAs. After liftoff, the transferred layer may then be alignedand bonded to the acceptor substrate or wafer. The manufacturability ofthe ELO process for multilayer layer transfer use was recently improvedby J. Yoon, et. al., of the University of Illinois at Urbana-Champaignas described in Nature May 20, 2010. Canon developed a layer transfertechnology called ELTRAN—Epitaxial Layer TRANsfer from porous silicon.ELTRAN may be utilized. The Electrochemical Society Meeting abstract No.438 from year 2000 and the JSAP International July 2001 paper show aseed wafer being anodized in an HF/ethanol solution to create pores inthe top layer of silicon, the pores may be treated with a lowtemperature oxidation and then high temperature hydrogen annealed toseal the pores. Epitaxial silicon may then be deposited on top of theporous silicon and then oxidized to form the SOI BOX. The seed wafer maybe bonded to a handle wafer and the seed wafer may be split off by highpressure water directed at the porous silicon layer. The porous siliconmay then be selectively etched off leaving a uniform silicon layer.

FIG. 2 is a drawing illustration of a layer transfer process flow. Inanother illustrative embodiment of the invention, “Layer-Transfer” maybe used for construction of the underlying circuitry of Foundation layer114. Wafer 202 may include a monocrystalline silicon wafer that wasprocessed to construct the underlying circuitry. The wafer 202 could beof the most advanced process or more likely a few generations behind. Itcould include the programming circuits of Foundation layer 114 and otheruseful structures and may be a preprocessed CMOS silicon wafer, or apartially processed CMOS, or other prepared silicon or semiconductorsubstrate. Wafer 202 may also be called an acceptor substrate or atarget wafer. An oxide layer 212 may then be deposited on top of thewafer 202 and thereafter may be polished for better planarization andsurface preparation. A donor wafer 206 may then be brought in to bebonded to wafer 202. The surfaces of both donor wafer 206 and wafer 202may be pre-processed for low temperature bonding by various surfacetreatments, such as an RCA pre-clean that may comprise dilute ammoniumhydroxide or hydrochloric acid, and may include plasma surfacepreparations to lower the bonding energy and enhance the wafer to waferbond strength. The donor wafer 206 may be pre-prepared for “SmartCut” byan ion implant of an atomic species, such as H+ ions, at the desireddepth to prepare the SmartCut line 208. SmartCut line 208 may also becalled a layer transfer demarcation plane, shown as a dashed line. TheSmartCut line 208 or layer transfer demarcation plane may be formedbefore or after other processing on the donor wafer 206. Donor wafer 206may be bonded to wafer 202 by bringing the donor wafer 206 surface inphysical contact with the wafer 202 surface, and then applyingmechanical force and/or thermal annealing to strengthen the oxide tooxide bond. Alignment of the donor wafer 206 with the wafer 202 may beperformed immediately prior to the wafer bonding. Acceptable bondstrengths may be obtained with bonding thermal cycles that do not exceedabout 400° C. After bonding the two wafers a SmartCut step may beperformed to cleave and remove the top portion 214 of the donor wafer206 along the SmartCut line 208. The cleaving may be accomplished byvarious applications of energy to the SmartCut line 208, or layertransfer demarcation plane, such as a mechanical strike by a knife orjet of liquid or jet of air, or by local laser heating, by applicationof ultrasonic or megasonic energy, or other suitable methods. The resultmay be a 3D wafer 210 which may include wafer 202 with a transferredsilicon layer 204 of mono-crystalline silicon, or multiple layers ofmaterials. Transferred silicon layer 204 may be polished chemically andmechanically to provide a suitable surface for further processing.Transferred silicon layer 204 could be quite thin at the range of about50-200 nm. The described flow may be called “layer transfer”. Layertransfer may be commonly utilized in the fabrication of SOI—Silicon OnInsulator—wafers. For SOI wafers the upper surface may be oxidized sothat after “layer transfer” a buried oxide—BOX—may provide isolationbetween the top thin mono-crystalline silicon layer and the bulk of thewafer. The use of an implanted atomic species, such as Hydrogen orHelium or a combination, to create a cleaving plane as described abovemay be referred to in this document as “SmartCut” or “ion-cut” and maybe generally the illustrated layer transfer method.

Persons of ordinary skill in the art will appreciate that theillustrations in FIG. 2 are exemplary only and are not drawn to scale.Such skilled persons will further appreciate that many variations may bepossible such as, for example, a heavily doped (greater than 1e20atoms/cm3) boron layer or silicon germanium (SiGe) layer may be utilizedas an etch stop either within the ion-cut process flow, wherein thelayer transfer demarcation plane may be placed within the etch stoplayer or into the substrate material below, or the etch stop layers maybe utilized without an implant cleave process and the donor wafer maybe, for example, etched away until the etch stop layer is reached. Suchskilled persons will further appreciate that the oxide layer within anSOI or GeOI donor wafer may serve as the etch stop layer, and hence oneedge of the oxide layer may function as a layer transfer demarcationplane. Moreover, the dose and energy of the implanted specie or speciesmay be uniform across the surface area of the wafer or may have adeliberate variation, including, for example, a higher dose of hydrogenat the edges of a monocrystalline silicon wafer to promote cleaving.Many other modifications within the scope of the illustrated embodimentsof the invention will suggest themselves to such skilled persons afterreading this specification. Thus the invention is to be limited only bythe appended claims.

Now that a “layer transfer” process may be used to bond a thinmono-crystalline silicon layer transferred silicon layer 204 on top ofthe preprocessed wafer 202, a standard process could ensue to constructthe rest of the desired circuits as illustrated in FIG. 1A, startingwith primary silicon layer 102A on the transferred silicon layer 204.The lithography step may use alignment marks on wafer 202 so thefollowing circuits of primary silicon layer 102A and logic fabric/firstantifuse layer 104 and so forth could be properly connected to theunderlying circuits of Foundation layer 114. An aspect that should beaccounted for is the high temperature that may be needed for theprocessing of circuits of primary silicon layer 102A. The pre-processedcircuits on wafer 202 may need to withstand this high temperatureassociated with the activation of the semiconductor transistors ofprimary silicon layer 102A fabricated on the transferred silicon layer204. Those circuits on wafer 202 may include transistors and localinterconnects of poly-crystalline silicon (polysilicon or poly) and someother type of interconnection that could withstand high temperature suchas tungsten. A processed wafer that can withstand subsequent processingof transistors on top at high temperatures may be a called the“Foundation” or a foundation wafer, layer or circuitry. An illustratedadvantage of using layer transfer for the construction of the underlyingcircuits may include having the transferred silicon layer 204 be verythin which may enable the through silicon via connections 116, orthrough layer vias (TLVs), to have low aspect ratios and be more likenormal contacts, which could be made very small and with minimum areapenalty. The thin transferred layer may also allow conventional directthrough-layer alignment techniques to be performed, thus increasing thedensity of through silicon via connections 116.

There may be a few alternative methods to construct the top transistorsprecisely aligned to the underlying pre-fabricated layers such aspre-processed wafer or layer 108, utilizing “SmartCut” layer transferand not exceeding the temperature limit, typically about 400° C., of theunderlying pre-fabricated structure, which may include low meltingtemperature metals or other construction materials such as, for example,aluminum or copper. As the layer transfer may be less than about 200 nmthick, then the transistors defined on it could be aligned precisely tothe top metal layer of the pre-processed wafer or layer 108 as may beneeded and those transistors may have state of the art layer to layermisalignment capability, for example, less than about 40 nm misalignmentor less than about 4 nm misalignment, as well as through layer via, orlayer to layer metal connection, diameters of less than about 50 nm, oreven less than about 20 nm. The thinner the transferred layer, thesmaller the through layer via diameter obtainable, due to the potentiallimitations of manufacturable via aspect ratios. The transferred layermay be, for example, less than about 2 microns thick, less than about 1micron thick, less than about 0.4 microns thick, less than about 200 nmthick, or less than about 100 nm thick.

The term alignment mark in the use herein may be defined as “an imageselectively placed within or outside an array for either testing oraligning, or both [ASTM F127-84], also called alignment key andalignment target,” as in the SEMATECH dictionary. The alignment markmay, for example, be within a layer, wafer, or substrate of materialprocessing or to be processed, and/or may be on a photomask orphotoresist image, or may be a calculated position within, for example,a lithographic wafer stepper's software or memory.

Novel monolithic 3D memory technologies utilizing material resistancechanges may be constructed in a similar manner. There may be many typesof resistance-based memories including phase change memory, Metal Oxidememory, resistive RAM (RRAM), memristors, solid-electrolyte memory,ferroelectric RAM, MRAM, etc. Background information on theseresistive-memory types may be given in “Overview of candidate devicetechnologies for storage-class memory,” IBM Journal of Research andDevelopment, vol. 52, no. 4.5, pp. 449-464, July 2008 by Burr, G. W.,et. al. The contents of this document are incorporated in thisspecification by reference.

As illustrated in FIGS. 3A to 3K, a resistance-based zero additionalmasking steps per memory layer 3D memory may be constructed that issuitable for 3D IC manufacturing. This 3D memory may utilizejunction-less transistors and may have a resistance-based memory elementin series with a select or access transistor.

As illustrated in FIG. 3A, a silicon substrate with peripheral circuitry302 may be constructed with high temperature (greater than about 400°C.) resistant wiring, such as, for example, Tungsten. The peripheralcircuitry substrate 302 may include memory control circuits as well ascircuitry for other purposes and of various types, such as, for example,analog, digital, RF, or memory. The peripheral circuitry substrate 302may include peripheral circuits that can withstand an additionalrapid-thermal-anneal (RTA) and still remain operational and retain goodperformance. For this purpose, the peripheral circuits may be formedsuch that they have had a weak RTA or no RTA for activating dopants. Thetop surface of the peripheral circuitry substrate 302 may be preparedfor oxide wafer bonding with a deposition of a silicon oxide layer 304,thus forming acceptor wafer 314.

As illustrated in FIG. 3B, a mono-crystalline silicon donor wafer 312may be, for example, processed to include a wafer sized layer of N+doping (not shown) which may have a different dopant concentration thanthe N+ substrate 306. The N+ doping layer may be formed by ionimplantation and thermal anneal A screen oxide layer 308 may be grown ordeposited prior to the implant to protect the silicon from implantcontamination and to provide an oxide surface for later wafer to waferbonding A layer transfer demarcation plane 310 (shown as a dashed line)may be formed in donor wafer 312 within the N+ substrate 306 or the N+doping layer (not shown) by hydrogen implantation or other methods aspreviously described. Both the donor wafer 312 and acceptor wafer 314may be prepared for wafer bonding as previously described and thenbonded at the surfaces of oxide layer 304 and oxide layer 308, at a lowtemperature (less than about 400° C.) suitable for lowest stresses, or amoderate temperature (less than about 900° C.).

As illustrated in FIG. 3C, the portion of the N+ layer (not shown) andthe N+ wafer substrate 306 that are above the layer transfer demarcationplane 310 may be removed by cleaving and polishing, or other processesas previously described, such as, for example, ion-cut or other methods,thus forming the remaining mono-crystalline silicon N+ layer 306′.Remaining N+ layer 306′ and oxide layer 308 may have been layertransferred to acceptor wafer 314. The top surface of N+ layer 306′ maybe chemically or mechanically polished smooth and flat. Now transistorsor portions of transistors may be formed and aligned to the acceptorwafer 314 alignment marks (not shown). Oxide layer 320 may be depositedto prepare the surface for later oxide to oxide bonding, leading to theformation of the first Si/SiO2 layer 323 that includes silicon oxidelayer 320, N+ silicon layer 306′, and oxide layer 308.

As illustrated in FIG. 3D, additional Si/SiO2 layers, such as, forexample, second Si/SiO2 layer 325 and third Si/SiO2 layer 327, may eachbe formed as described in FIGS. 3A to 3C. Oxide layer 329 may bedeposited to electrically isolate the top N+ silicon layer.

As illustrated in FIG. 3E, oxide layer 329, third Si/SiO2 layer 327,second Si/SiO2 layer 325 and first Si/SiO2 layer 323 may belithographically defined and plasma/RIE etched to form a portion of thememory cell structure, which may now include regions of N+ silicon 326and oxide 322. Thus, these transistor elements or portions may have beendefined by a common lithography step, which also may be described as asingle lithography step, same lithography step, or one lithography step.

As illustrated in FIG. 3F, a gate dielectric and gate electrode materialmay be deposited, planarized with a chemical mechanical polish (CMP),and may then be lithographically defined and plasma/RIE etched to formgate dielectric regions 328 which may either be self-aligned to andcovered by gate electrodes 330 (shown), or cover the entire N+ silicon326 and oxide 322 multi-layer structure. The gate stack including gateelectrode 330 and gate dielectric 328 may be formed with a gatedielectric, such as, for example, thermal oxide, and a gate electrodematerial, such as, for example, poly-crystalline silicon. Alternatively,the gate dielectric may be an atomic layer deposited (ALD) material thatmay be paired with a work function specific gate metal according toindustry standard high k metal gate process schemes describedpreviously. Moreover, the gate dielectric may be formed with a rapidthermal oxidation (RTO), a low temperature oxide deposition or lowtemperature microwave plasma oxidation of the silicon surfaces and thena gate electrode such as, for example, tungsten or aluminum may bedeposited.

As illustrated in FIG. 3G, the entire structure may be covered with agap fill oxide 332, which may be planarized with chemical mechanicalpolishing. The oxide 332 is shown transparent in the figure for clarityin illustration. Also shown are word-line regions (WL) 350, coupled withand composed of gate electrodes 330, and source-line regions (SL) 352,composed of N+ silicon regions 326.

As illustrated in FIG. 3H, bit-line (BL) contacts 334 may belithographically defined, etched along with plasma/RIE through oxide332, the three N+ silicon regions 326, and associated oxide verticalisolation regions to connect all memory layers vertically. BL contacts334 may then be processed by a photoresist removal. Resistive changematerial 338, such as, for example, hafnium oxide, may then bedeposited, for example, with atomic layer deposition (ALD). Theelectrode for the resistance change memory element may then be depositedby ALD to form the electrode/BL contact 334. The excess depositedmaterial may be polished to planarity at or below the top of oxide 332.Each BL contact 334 with resistive change material 338 may be sharedamong substantially all layers of memory, shown as three layers ofmemory in FIG. 3H.

As illustrated in FIG. 3I, BL metal lines 336 may be formed and mayconnect to the associated BL contacts 334 with resistive change material338. Contacts and associated metal interconnect lines (not shown) may beformed for the WL and SL at the memory array edges. A through layer via(not shown) may be formed to electrically couple the BL, SL, and WLmetallization to the acceptor wafer 314 peripheral circuitry via anacceptor wafer metal connect pad (not shown).

FIG. 3J1 shows a cross sectional cut II of FIG. 3J, while FIG. 3J2 showsa cross-sectional cut III of FIG. 3J. FIG. 3J1 shows BL metal line 336,oxide 332, BL contact/electrode 334, resistive change material 338, WLregions 350, gate dielectric 328, N+ silicon regions 326, and peripheralcircuitry substrate 302. The BL contact/electrode 334 may couple to oneside of the three levels of resistive change material 338. The otherside of the resistive change material 338 may be coupled to N+ regions326. FIG. 3J2 shows BL metal lines 336, oxide 332, gate electrode 330,gate dielectric 328, N+ silicon regions 326, interlayer oxide region(‘ox’), and peripheral circuitry substrate 302. The gate electrode 330may be common to substantially all six N+ silicon regions 326 and mayform six two-sided gated junction-less transistors as memory selecttransistors.

As illustrated in FIG. 3K, a single exemplary two-sided gatejunction-less transistor on the first Si/SiO2 layer 323 may include N+silicon region 326 (functioning as the source, drain, and transistorchannel), and two gate electrodes 330 with associated gate dielectrics328. The transistor may be electrically isolated from beneath by oxidelayer 308.

This flow may enable the formation of a resistance-based multi-layer or3D memory array with zero additional masking steps per memory layer,which may utilize junction-less transistors and may have aresistance-based memory element in series with a select transistor, andmay be constructed by layer transfers of wafer sized dopedmono-crystalline silicon layers, and this 3D memory array may beconnected to an underlying multi-metal layer semiconductor device.

Persons of ordinary skill in the art will appreciate that theillustrations in FIGS. 3A through 3K are exemplary only and are notdrawn to scale. Such skilled persons will further appreciate that manyvariations may be possible such as, for example, the transistors may beof another type such as RCATs. Additionally, doping of each N+ layer maybe slightly different to compensate for interconnect resistances.Moreover, the stacked memory layer may be connected to a peripherycircuit that may be above the memory stack. Further, each gate of thedouble gate 3D resistance based memory can be independently controlledfor better control of the memory cell. Many other modifications withinthe scope of the illustrated embodiments of the invention will suggestthemselves to such skilled persons after reading this specification.Thus the invention is to be limited only by the appended claims.

As illustrated in FIGS. 4A to 4G, a charge trap based 3D memory withzero additional masking steps per memory layer 3D memory may beconstructed that may be suitable for 3D IC manufacturing. This 3D memorymay utilize NAND strings of charge trap junction-less transistors withjunction-less select transistors constructed in mono-crystallinesilicon.

As illustrated in FIG. 4A, a silicon substrate with peripheral circuitry402 may be constructed with high temperature (e.g., greater than about400° C.) resistant wiring, such as, for example, Tungsten. Theperipheral circuitry substrate 402 may include memory control circuitsas well as circuitry for other purposes and of various types, such as,for example, analog, digital, RF, or memory. The peripheral circuitrysubstrate 402 may include peripheral circuits that can withstand anadditional rapid-thermal-anneal (RTA) or flash anneal and still remainoperational and retain good performance. For this purpose, theperipheral circuits may be formed such that they have been subject to aweak RTA or no RTA for activating dopants. The top surface of theperipheral circuitry substrate 402 may be prepared for oxide waferbonding with a deposition of a silicon oxide layer 404, thus formingacceptor substrate 414.

As illustrated in FIG. 4B, a mono-crystalline silicon donor wafer 412may be processed to include a wafer sized layer of N+ doping (not shown)which may have a different dopant concentration than the N+ substrate406. The N+ doping layer may be formed by ion implantation and thermalanneal. A screen oxide layer 408 may be grown or deposited prior to theimplant to protect the silicon from implant contamination and to providean oxide surface for later wafer to wafer bonding. A layer transferdemarcation plane 410 (shown as a dashed line) may be formed in donorwafer 412 within the N+ substrate 406 or the N+ doping layer (not shown)by hydrogen implantation or other methods as previously described. Boththe donor wafer 412 and acceptor substrate 414 may be prepared for waferbonding as previously described and then bonded at the surfaces of oxidelayer 404 and oxide layer 408, at a low temperature (e.g., less thanabout 400° C. suitable for lowest stresses), or a moderate temperature(e.g., less than about 900° C.).

As illustrated in FIG. 4C, the portion of the N+ layer (not shown) andthe N+ wafer substrate 406 that may be above the layer transferdemarcation plane 410 may be removed by cleaving and polishing, or otherprocesses as previously described, such as ion-cut or other methods,thus forming the remaining mono-crystalline silicon N+ layer 406′.Remaining N+ layer 406′ and oxide layer 408 may have been layertransferred to acceptor substrate 414. The top surface of N+ layer 406′may be chemically or mechanically polished smooth and flat. Oxide layer420 may be deposited to prepare the surface for later oxide to oxidebonding. This bonding may now form the first Si/SiO2 layer 423 includingsilicon oxide layer 420, N+ silicon layer 406′, and oxide layer 408.

As illustrated in FIG. 4D, additional Si/SiO2 layers, such as, forexample, second Si/SiO2 layer 425 and third Si/SiO2 layer 427, may eachbe formed as described in FIGS. 4A to 4C. Oxide layer 429 may bedeposited to electrically isolate the top N+ silicon layer.

As illustrated in FIG. 4E, oxide layer 429, third Si/SiO2 layer 427,second Si/SiO2 layer 425 and first Si/SiO2 layer 423 may belithographically defined and plasma/RIE etched to form a portion of thememory cell structure, which may now include regions of N+ silicon 426and oxide 422. Thus, these transistor elements or portions may have beendefined by a common lithography step, which also may be described as asingle lithography step, same lithography step, or one lithography step.

As illustrated in FIG. 4F, a gate stack may be formed with growth ordeposition of a charge trap gate dielectric layer, such as thermal oxideand silicon nitride layers (ONO: Oxide-Nitride-Oxide), and a gate metalelectrode layer, such as doped or undoped poly-crystalline silicon. Thegate metal electrode layer may then be planarized with chemicalmechanical polishing. Alternatively, the charge trap gate dielectriclayer may include silicon or III-V nano-crystals encased in an oxide.The select transistor area 438 may include a non-charge trap dielectric.The gate metal electrode regions 430 and gate dielectric regions 428 ofboth the NAND string area 436 and select transistor area 438 may belithographically defined and plasma/RIE etched.

As illustrated in FIG. 4G, the entire structure may be covered with agap fill oxide 432, which may be planarized with chemical mechanicalpolishing. The gap fill oxide 432 is shown transparent in the figure forclarity in illustration. Select metal lines 446 may be formed andconnected to the associated select gate contacts 434. Contacts andassociated metal interconnect lines (not shown) may be formed for the WLand SL at the memory array edges. Word-line regions (WL) 436, gate metalelectrode regions 430, and bit-line regions (BL) 452 including indicatedN+ silicon regions 426, are shown. Source regions 444 may be formed by atrench contact etch and filled to couple to the N+ silicon regions onthe source end of the NAND string 436. A through layer via (not shown)may be formed to electrically couple the BL, SL, and WL metallization tothe acceptor substrate 414 peripheral circuitry via an acceptor wafermetal connect pad (not shown).

This flow may enable the formation of a charge trap based 3D memory withzero additional masking steps per memory layer constructed by layertransfers of wafer sized doped layers of mono-crystalline silicon andthis 3D memory may be connected to an underlying multi-metal layersemiconductor device.

Persons of ordinary skill in the art will appreciate that theillustrations in FIGS. 4A through 4G are exemplary only and are notdrawn to scale. Such skilled persons will further appreciate that manyvariations may be possible such as, for example, BL or SL contacts maybe constructed in a staircase manner as described previously and in theincorporated documents. Moreover, the stacked memory layer may beconnected to a periphery circuit that may be above the memory stack.Additionally, each tier of memory could be configured with a slightlydifferent donor wafer N+ layer doping profile. Further, the memory couldbe organized in a different manner, such as BL and SL interchanged, orwhere buried wiring for the memory array may be below the memory layersbut above the periphery. Additional types of 3D charge trap memories maybe constructed by layer transfer of mono-crystalline silicon; forexample, those found in “A Highly Scalable 8-Layer 3D Vertical-Gate (VG)TFT NAND Flash Using Junction-Free Buried Channel BE-SONOS Device,”Symposium on VLSI Technology, 2010 by Hang-Ting Lue, et al., and“Multi-layered Vertical Gate NAND Flash overcoming stacking limit forterabit density storage”, Symposium on VLSI Technology, 2009 by W. Kim,S. Choi, et al. Many other modifications within the scope of theillustrated embodiments of the invention will suggest themselves to suchskilled persons after reading this specification. Thus the invention isto be limited only by the appended claims.

The monolithic 3D integration concepts described in this patentapplication can lead to novel embodiments of poly-crystalline siliconbased memory architectures. While the following concepts in FIGS. 5 and6 are explained by using resistive memory architectures as an example,it will be clear to one skilled in the art that similar concepts can beapplied to the NAND flash, charge trap, and DRAM memory architecturesand process flows described previously in this patent application.

As illustrated in FIGS. 5A to 5K, a resistance-based 3D memory with zeroadditional masking steps per memory layer may be constructed withmethods that may be suitable for 3D IC manufacturing. This 3D memory mayutilize poly-crystalline silicon junction-less transistors that may haveeither a positive or a negative threshold voltage and may have aresistance-based memory element in series with a select or accesstransistor.

As illustrated in FIG. 5A, a silicon substrate with peripheral circuitry502 may be constructed with high temperature (greater than about 400°C.) resistant wiring, such as, for example, Tungsten. The peripheralcircuits substrate 502 may include memory control circuits as well ascircuitry for other purposes and of various types, such as, for example,analog, digital, RF, or memory. The peripheral circuits substrate 502may include peripheral circuits that can withstand an additionalrapid-thermal-anneal (RTA) or flash anneal and may still remainoperational and retain good performance. For this purpose, theperipheral circuits may be formed such that they have been subject to apartial or weak RTA or no RTA for activating dopants. Silicon oxidelayer 504 may be deposited on the top surface of the peripheralcircuitry substrate.

As illustrated in FIG. 5B, a layer of N+ doped poly-crystalline oramorphous silicon 506 may be deposited. The amorphous silicon orpoly-crystalline silicon layer 506 may be deposited using a chemicalvapor deposition process, such as LPCVD or PECVD, or other processmethods, and may be deposited doped with N+ dopants, such as Arsenic orPhosphorous, or may be deposited un-doped and subsequently doped with,such as, ion implantation or PLAD (PLasma Assisted Doping) techniques.Silicon Oxide 520 may then be deposited or grown. This oxide may nowform the first Si/SiO2 layer 523 which may include N+ dopedpoly-crystalline or amorphous silicon layer 506 and silicon oxide layer520.

As illustrated in FIG. 5C, additional Si/SiO2 layers, such as, forexample, second Si/SiO2 layer 525 and third Si/SiO2 layer 527, may eachbe formed as described in FIG. 5B. Oxide layer 529 may be deposited toelectrically isolate the top N+ doped poly-crystalline or amorphoussilicon layer.

As illustrated in FIG. 5D, a Rapid Thermal Anneal (RTA) or flash annealmay be conducted to crystallize the N+ doped poly-crystalline silicon oramorphous silicon layers 506 of first Si/SiO2 layer 523, second Si/SiO2layer 525, and third Si/SiO2 layer 527, forming crystallized N+ siliconlayers 516. Temperatures during this RTA may be as high as about 800° C.Alternatively, an optical anneal, such as, for example, a laser anneal,could be performed alone or in combination with the RTA or otherannealing processes.

As illustrated in FIG. 5E, oxide layer 529, third Si/SiO2 layer 527,second Si/SiO2 layer 525 and first Si/SiO2 layer 523 may belithographically defined and plasma/RIE etched to form a portion of thememory cell structure, which may now include multiple layers of regionsof crystallized N+ silicon 526 (previously crystallized N+ siliconlayers 516) and oxide 522. Thus, these transistor elements or portionsmay have been defined by a common lithography step, which also may bedescribed as a single lithography step, same lithography step, or onelithography step.

As illustrated in FIG. 5F, a gate dielectric and gate electrode materialmay be deposited, planarized with a chemical mechanical polish (CMP),and then lithographically defined and plasma/RIE etched to form gatedielectric regions 528 which may either be self-aligned to and coveredby gate electrodes 530 (shown), or cover the entire crystallized N+silicon regions 526 and oxide regions 522 multi-layer structure. Thegate stack including gate electrode 530 and gate dielectric regions 528may be formed with a gate dielectric, such as thermal oxide, and a gateelectrode material, such as poly-crystalline silicon. Alternatively, thegate dielectric may be an atomic layer deposited (ALD) material that maybe paired with a work function specific gate metal according to industrystandard high k metal gate process schemes described previously.Furthermore, the gate dielectric may be formed with a rapid thermaloxidation (RTO), a low temperature oxide deposition or low temperaturemicrowave plasma oxidation of the silicon surfaces and then a gateelectrode such as tungsten or aluminum may be deposited.

As illustrated in FIG. 5G, the entire structure may be covered with agap fill oxide 532, which may be planarized with chemical mechanicalpolishing. The oxide 532 is shown transparently in the figure forclarity in illustration. Also shown are word-line regions (WL) 550,which may be coupled with and include gate electrodes 530, andsource-line regions (SL) 552, including crystallized N+ silicon regions526.

As illustrated in FIG. 5H, bit-line (BL) contacts 534 may belithographically defined, etched with plasma/RIE through oxide 532, thethree crystallized N+ silicon regions 526, and associated oxide verticalisolation regions, to connect substantially all memory layersvertically, and then photoresist may be removed. Resistance changematerial 538, such as, for example, hafnium oxides or titanium oxides,may then be deposited, for example, with atomic layer deposition (ALD).The electrode for the resistance change memory element may then bedeposited by ALD to form the electrode/BL contact 534. The excessdeposited material may be polished to planarity at or below the top ofoxide 532. Each BL contact 534 with resistive change material 538 may beshared among substantially all layers of memory, shown as three layersof memory in FIG. 5H.

As illustrated in FIG. 5I, BL metal lines 536 may be formed andconnected to the associated BL contacts 534 with resistive changematerial 538. Contacts and associated metal interconnect lines (notshown) may be formed for the WL and SL at the memory array edges. Athrough layer via (not shown) may be formed to electrically couple theBL, SL, and WL metallization to the acceptor substrate peripheralcircuitry via an acceptor wafer metal connect pad (not shown).

FIG. 5J1 is a cross sectional cut II view of FIG. 5J, while FIG. 5J2 isa cross sectional cut III view of FIG. 5J. FIG. 5J1 shows BL metal line536, oxide 532, BL contact/electrode 534, resistive change material 538,WL regions 550, gate dielectric regions 528, crystallized N+ siliconregions 526, and peripheral circuits substrate 502. The BLcontact/electrode 534 may couple to one side of the three levels ofresistive change material 538. The other side of the resistive changematerial 538 may be coupled to crystallized N+ regions 526. FIG. 5J2shows BL metal lines 536, oxide 532, gate electrode 530, gate dielectricregions 528, crystallized N+ silicon regions 526, interlayer oxideregion (‘ox’), and peripheral circuits substrate 502. The gate electrode530 may be common to substantially all six crystallized N+ siliconregions 526 and may form six two-sided gated junction-less transistorsas memory select transistors.

As illustrated in FIG. 5K, a single exemplary two-sided gatedjunction-less transistor on the first Si/SiO2 layer 523 may includecrystallized N+ silicon region 526 (functioning as the source, drain,and transistor channel), and two gate electrodes 530 with associatedgate dielectric regions 528. The transistor may be electrically isolatedfrom beneath by oxide layer 508.

This flow may enable the formation of a resistance-based multi-layer or3D memory array with zero additional masking steps per memory layer,which may utilize poly-crystalline silicon junction-less transistors andmay have a resistance-based memory element in series with a selecttransistor, and may be constructed by layer transfer of wafer sizeddoped poly-crystalline silicon layers, and this 3D memory array may beconnected to an underlying multi-metal layer semiconductor device.

Persons of ordinary skill in the art will appreciate that theillustrations in FIGS. 5A through 5K are exemplary only and are notdrawn to scale. Such skilled persons will further appreciate that manyvariations may be possible such as, for example, the RTAs and/or opticalanneals of the N+ doped poly-crystalline or amorphous silicon layers 506as described for FIG. 5D may be performed after each Si/SiO2 layer isformed in FIG. 5C. Additionally, N+ doped poly-crystalline or amorphoussilicon layer 506 may be doped P+, or with a combination of dopants andother polysilicon network modifiers to enhance the RTA or opticalannealing and subsequent crystallization and lower the N+ silicon layer516 resistivity. Moreover, doping of each crystallized N+ layer may beslightly different to compensate for interconnect resistances.Furthermore, each gate of the double gated 3D resistance based memorymay be independently controlled for better control of the memory cell.Many other modifications within the scope of the illustrated embodimentsof the invention will suggest themselves to such skilled persons afterreading this specification. Thus the invention is to be limited only bythe appended claims.

As illustrated in FIGS. 6A to 6J, an alternative embodiment of aresistance based 3D memory with zero additional masking steps per memorylayer may be constructed with methods that are suitable for 3D ICmanufacturing. This 3D memory may utilize poly-crystalline siliconjunction-less transistors that may have either a positive or a negativethreshold voltage, a resistance-based memory element in series with aselect or access transistor, and may have the periphery circuitry layerformed or layer transferred on top of the 3D memory array.

As illustrated in FIG. 6A, a silicon oxide layer 604 may be deposited orgrown on top of silicon substrate 602.

As illustrated in FIG. 6B, a layer of N+ doped poly-crystalline oramorphous silicon 606 may be deposited. The N+ doped poly-crystalline oramorphous silicon layer 606 may be deposited using a chemical vapordeposition process, such as LPCVD or PECVD, or other process methods,and may be deposited doped with N+ dopants, such as, for example,Arsenic or Phosphorous, or may be deposited un-doped and subsequentlydoped with, such as, for example, ion implantation or PLAD (PLasmaAssisted Doping) techniques. Silicon Oxide 620 may then be deposited orgrown. This oxide may now form the first Si/SiO2 layer 623 comprised ofN+ doped poly-crystalline or amorphous silicon layer 606 and siliconoxide layer 620.

As illustrated in FIG. 6C, additional Si/SiO2 layers, such as, forexample, second Si/SiO2 layer 625 and third Si/SiO2 layer 627, may eachbe formed as described in FIG. 6B. Oxide layer 629 may be deposited toelectrically isolate the top N+ doped poly-crystalline or amorphoussilicon layer.

As illustrated in FIG. 6D, a Rapid Thermal Anneal (RTA) or flash annealmay be conducted to crystallize the N+ doped poly-crystalline silicon oramorphous silicon layers 606 of first Si/SiO2 layer 623, second Si/SiO2layer 625, and third Si/SiO2 layer 627, forming crystallized N+ siliconlayers 616. Alternatively, an optical anneal, such as, for example, alaser anneal, could be performed alone or in combination with the RTA orother annealing processes. Temperatures during this step could be ashigh as about 700° C., and could even be as high as, for example, 1400°C. Since there may be no circuits or metallization underlying theselayers of crystallized N+ silicon, very high temperatures (such as, forexample, 1400° C.) can be used for the anneal process, leading to verygood quality poly-crystalline silicon with few grain boundaries and veryhigh carrier mobilities approaching those of mono-crystalline crystalsilicon.

As illustrated in FIG. 6E, oxide layer 629, third Si/SiO2 layer 627,second Si/SiO2 layer 625 and first Si/SiO2 layer 623 may belithographically defined and plasma/RIE etched to form a portion of thememory cell structure, which may now include multiple layers of regionsof crystallized N+ silicon 626 (previously crystallized N+ siliconlayers 616) and oxide 622. Thus, these transistor elements or portionsmay have been defined by a common lithography step, which also may bedescribed as a single lithography step, same lithography step, or onelithography step.

As illustrated in FIG. 6F, a gate dielectric and gate electrode materialmay be deposited, planarized with a chemical mechanical polish (CMP),and then lithographically defined and plasma/RIE etched to form gatedielectric regions 628 which may either be self-aligned to and coveredby gate electrodes 630 (shown), or cover the entire crystallized N+silicon regions 626 and oxide regions 622 multi-layer structure. Thegate stack including gate electrode 630 and gate dielectric regions 628may be formed with a gate dielectric, such as thermal oxide, and a gateelectrode material, such as poly-crystalline silicon. Alternatively, thegate dielectric may be an atomic layer deposited (ALD) material that maybe paired with a work function specific gate metal according to industrystandard high k metal gate process schemes described previously.Additionally, the gate dielectric may be formed with a rapid thermaloxidation (RTO), a low temperature oxide deposition or low temperaturemicrowave plasma oxidation of the silicon surfaces and then a gateelectrode such as tungsten or aluminum may be deposited.

As illustrated in FIG. 6G, the entire structure may be covered with agap fill oxide 632, which may be planarized with chemical mechanicalpolishing. The oxide 632 is shown transparently in the figure forclarity in illustration. Also shown are word-line regions (WL) 650,which may be coupled with and include gate electrodes 630, andsource-line regions (SL) 652, including crystallized N+ silicon regions626.

As illustrated in FIG. 6H, bit-line (BL) contacts 634 may belithographically defined, etched with, for example, plasma/RIE, throughoxide 632, the three crystallized N+ silicon regions 626, and theassociated oxide vertical isolation regions to connect substantially allmemory layers vertically. BL contacts 634 may then be processed by aphotoresist removal. Resistance change material 638, such as hafniumoxides or titanium oxides, may then be deposited, for example, withatomic layer deposition (ALD). The electrode for the resistance changememory element may then be deposited by ALD to form the electrode/BLcontact 634. The excess deposited material may be polished to planarityat or below the top of oxide 632. Each BL contact 634 with resistivechange material 638 may be shared among substantially all layers ofmemory, shown as three layers of memory in FIG. 6H.

As illustrated in FIG. 6I, BL metal lines 636 may be formed andconnected to the associated BL contacts 634 with resistive changematerial 638. Contacts and associated metal interconnect lines (notshown) may be formed for the WL and SL at the memory array edges.

As illustrated in FIG. 6J, peripheral circuits 678 may be constructedand then layer transferred, using methods described previously such as,for example, ion-cut with replacement gates, to the memory array. Thrulayer vias (not shown) may be formed to electrically couple theperiphery circuitry to the memory array BL, WL, SL and other connectionssuch as, for example, power and ground. Alternatively, the peripherycircuitry may be formed and directly aligned to the memory array andsilicon substrate 602 utilizing the layer transfer of wafer sized dopedlayers and subsequent processing, such as, for example, thejunction-less, Recess Channel Array Transistor (RCAT), V-groove, orbipolar transistor formation flows as previously described inincorporated documents.

This flow may enable the formation of a resistance-based multi-layer or3D memory array with zero additional masking steps per memory layer,which may utilize poly-crystalline silicon junction-less transistors andmay have a resistance-based memory element in series with a selecttransistor, and may be constructed by layer transfers of wafer sizeddoped poly-crystalline silicon layers, and this 3D memory array may beconnected to an overlying multi-metal layer semiconductor device orperiphery circuitry.

Persons of ordinary skill in the art will appreciate that theillustrations in FIGS. 6A through 6J are exemplary only and are notdrawn to scale. Such skilled persons will further appreciate that manyvariations may be possible such as, for example, the RTAs and/or opticalanneals of the N+ doped poly-crystalline or amorphous silicon layers 606as described for FIG. 6D may be performed after each Si/SiO2 layer maybe formed in FIG. 6C. Additionally, N+ doped poly-crystalline oramorphous silicon layer 606 may be doped P+, or with a combination ofdopants and other polysilicon network modifiers to enhance the RTA oroptical annealing crystallization and subsequent crystallization, andlower the N+ silicon layer 616 resistivity. Moreover, doping of eachcrystallized N+ layer may be slightly different to compensate forinterconnect resistances. Further, each gate of the double gated 3Dresistance based memory may be independently controlled for bettercontrol of the memory cell. Furthermore, by proper choice of materialsfor memory layer transistors and memory layer wires (e.g., by usingtungsten and other materials that withstand high temperature processingfor wiring), standard CMOS transistors may be processed at hightemperatures (e.g., greater than about 400° C.) to form the peripherycircuits 678. Many other modifications within the scope of theillustrated embodiments of the invention will suggest themselves to suchskilled persons after reading this specification. Thus the invention isto be limited only by the appended claims.

In this document, various terms may have been used while generallyreferring to the element. For example, “house” may refer to the firstmono-crystalline layer with its transistors and metal interconnectionlayer or layers. This first mono-crystalline layer may have also beenreferred to as the main wafer and sometimes as the acceptor wafer andsometimes as the base wafer.

Some embodiments of the invention may include alternative techniques tobuild IC (Integrated Circuit) devices including techniques and methodsto construct 3D IC systems. Some embodiments of the invention may enabledevice solutions with far less power consumption than prior art. Thesedevice solutions could be very useful for the growing application ofmobile electronic devices and mobile systems, such as, for example,mobile phones, smart phone, and cameras. For example, incorporating the3D IC semiconductor devices according to some embodiments of theinvention within these mobile electronic devices and mobile systemscould provide superior mobile units that could operate much moreefficiently and for a much longer time than with prior art technology.

Smart mobile systems may be greatly enhanced by complex electronics at alimited power budget. The 3D technology described in the multipleembodiments of the invention would allow the construction of low powerhigh complexity mobile electronic systems. For example, it would bepossible to integrate into a small form function a complex logic circuitwith high density high speed memory utilizing some of the 3D DRAMembodiments of the invention and add some non-volatile 3D NAND chargetrap or RRAM described in some embodiments of the invention.

In U.S. application Ser. No. 12/903,862, filed by some of the inventorsand assigned to the same assignee, a 3D micro display and a 3D imagesensor are presented. Integrating one or both of these with complexlogic and or memory could be very effective for mobile system.Additionally, mobile systems could be customized to some specific marketapplications by integrating some embodiments of the invention.

Moreover, utilizing 3D programmable logic or 3D gate array as had beendescribed in some embodiments of the invention could be very effectivein forming flexible mobile systems.

The need to reduce power to allow effective use of limited batteryenergy and also the lightweight and small form factor derived by highlyintegrating functions with low waste of interconnect and substrate couldbe highly benefited by the redundancy and repair idea of the 3Dmonolithic technology as has been presented in embodiments of theinvention. This unique technology could enable a mobile device thatwould be lower cost to produce or would require lower power to operateor would provide a lower size or lighter carry weight, and combinationsof these 3D monolithic technology features may provide a competitive ordesirable mobile system.

Another unique market that may be addressed by some of the embodimentsof the invention could be a street corner camera with supportingelectronics. The 3D image sensor described in the Ser. No. 12/903,862application would be very effective for day/night and multi-spectrumsurveillance applications. The 3D image sensor could be supported byintegrated logic and memory such as, for example, a monolithic 3D ICwith a combination of image processing and image compression logic andmemory, both high speed memory such as 3D DRAM and high densitynon-volatile memory such as 3D NAND or RRAM or other memory, and othercombinations. This street corner camera application would require lowpower, low cost, and low size or any combination of these features, andcould be highly benefited from the 3D technologies described herein.

3D ICs according to some embodiments of the invention could enableelectronic and semiconductor devices with much a higher performance as aresult from the shorter interconnect as well as semiconductor deviceswith far more complexity via multiple levels of logic and providing theability to repair or use redundancy. The achievable complexity of thesemiconductor devices according to some embodiments of the inventioncould far exceed what may be practical with the prior art technology.These potential advantages could lead to more powerful computer systemsand improved systems that have embedded computers.

Some embodiments of the invention may enable the design of state of theart electronic systems at a greatly reduced non-recurring engineering(NRE) cost by the use of high density 3D FPGAs or various forms of 3Darray base ICs with reduced custom masks as described previously. Thesesystems could be deployed in many products and in many market segments.Reduction of the NRE may enable new product family or applicationdevelopment and deployment early in the product lifecycle by loweringthe risk of upfront investment prior to a market being developed. Theabove potential advantages may also be provided by various mixes such asreduced NRE using generic masks for layers of logic and other genericmasks for layers of memories and building a very complex system usingthe repair technology to overcome the inherent yield limitation. Anotherform of mix could be building a 3D FPGA and add on it 3D layers ofcustomizable logic and memory so the end system could have fieldprogrammable logic on top of the factory customized logic. There may bemany ways to mix the many innovative elements to form 3D IC to supportthe need of an end system, including using multiple devices wherein morethan one device incorporates elements of embodiments of the invention.An end system could benefit from a memory device utilizing embodimentsof the invention 3D memory integrated together with a high performance3D FPGA integrated together with high density 3D logic, and so forth.Using devices that can use one or multiple elements according to someembodiments of the invention may allow for better performance or lowerpower and other illustrative advantages resulting from the use of someembodiments of the invention to provide the end system with acompetitive edge. Such end system could be electronic based products orother types of systems that may include some level of embeddedelectronics, such as, for example, cars, and remote controlled vehicles.

Commercial wireless mobile communications have been developed for almostthirty years, and play a special role in today's information andcommunication technology Industries. The mobile wireless terminal devicehas become part of our life, as well as the Internet, and the mobilewireless terminal device may continue to have a more important role on aworldwide basis. Currently, mobile (wireless) phones are undergoing muchdevelopment to provide advanced functionality. The mobile phone networkis a network such as a GSM, GPRS, or WCDMA, 3G and 4G standards, and thenetwork may allow mobile phones to communicate with each other. The basestation may be for transmitting (and receiving) information to themobile phone.

A typical mobile phone system may include, for example, a processor, aflash memory, a static random access memory, a display, a removablememory, a radio frequency (RF) receiver/transmitter, an analog base band(ABB), a digital base band (DBB), an image sensor, a high-speedbi-directional interface, a keypad, a microphone, and a speaker. Atypical mobile phone system may include a multiplicity of an element,for example, two or more static random access memories, two or moredisplays, two or more RF receiver/transmitters, and so on.

Conventional radios used in wireless communications, such as radios usedin conventional cellular telephones, typically may include severaldiscrete RF circuit components. Some receiver architectures may employsuperhetrodyne techniques. In a superheterodyne architecture an incomingsignal may be frequency translated from its radio frequency (RF) to alower intermediate frequency (IF). The signal at IF may be subsequentlytranslated to baseband where further digital signal processing ordemodulation may take place. Receiver designs may have multiple IFstages. The reason for using such a frequency translation scheme is thatcircuit design at the lower IF frequency may be more manageable forsignal processing. It is at these IF frequencies that the selectivity ofthe receiver may be implemented, automatic gain control (AGC) may beintroduced, etc.

A mobile phone's need of a high-speed data communication capability inaddition to a speech communication capability has increased in recentyears. In GSM (Global System for Mobile communications), one of EuropeanMobile Communications Standards, GPRS (General Packet Radio Service) hasbeen developed for speeding up data communication by allowing aplurality of time slot transmissions for one time slot transmission inthe GSM with the multiplexing TDMA (Time Division Multiple Access)architecture. EDGE (Enhanced Data for GSM Evolution) architectureprovides faster communications over GPRS.

4th Generation (4G) mobile systems aim to provide broadband wirelessaccess with nominal data rates of 100 Mbit/s. 4G systems may be based onthe 3GPP LTE (Long Term Evolution) cellular standard, WiMax orFlash-OFDM wireless metropolitan area network technologies. The radiointerface in these systems may be based on all-IP packet switching, MIMOdiversity, multi-carrier modulation schemes, Dynamic Channel Assignment(DCA) and channel-dependent scheduling.

Prior art such as U.S. application Ser. No. 12/871,984 may provide adescription of a mobile device and its block-diagram.

It is understood that the use of specific component, device and/orparameter names (such as those of the executing utility/logic describedherein) are for example only and not meant to imply any limitations onthe invention. The invention may thus be implemented with differentnomenclature/terminology utilized to describe thecomponents/devices/parameters herein, without limitation Each termutilized herein is to be given its broadest interpretation given thecontext in which that term is utilized. For example, as utilized herein,the following terms are generally defined:

(1) Mobile computing/communication device (MCD): is a device that may bea mobile communication device, such as a cell phone, or a mobilecomputer that performs wired and/or wireless communication via aconnected wireless/wired network. In some embodiments, the MCD mayinclude a combination of the functionality associated with both types ofdevices within a single standard device (e.g., a smart phones orpersonal digital assistant (PDA)) for use as both a communication deviceand a computing device.

Some embodiments of the invention may include alternative techniques tobuild IC (Integrated Circuit) devices including techniques and methodsto construct 3D IC systems. Some embodiments of the invention may enabledevice solutions with far less power consumption than prior art, or withmore functionality in a smaller physical footprint. These devicesolutions could be very useful for the growing application of Autonomousin vivo Electronic Medical (AEM) devices and AEM systems such asingestible “camera pills,” implantable insulin dispensers, implantableheart monitoring and stimulating devices, and the like. One suchingestible “camera pill” is the Philips' remote control “iPill”. Forexample, incorporating the 3D IC semiconductor devices according to someembodiments of the invention within these AEM devices and systems couldprovide superior autonomous units that could operate much moreeffectively and for a much longer time than with prior art technology.Sophisticated AEM systems may be greatly enhanced by complex electronicswith limited power budget. The 3D technology described in many of theembodiments of the invention would allow the construction of a low powerhigh complexity AEM system. For example it would be possible tointegrate into a small form function a complex logic circuit with highdensity high speed memory utilizing some of the 3D DRAM embodimentsherein and to add some non-volatile 3D NAND charge trap or RRAMdescribed in embodiments herein. Also in another application Ser. No.12/903,862 filed by some of the inventors and assigned to the sameassignee a 3D micro display and a 3D image sensor are presented.Integrating one or both to complex logic and or memory could be veryeffective for retinal implants. Additional AEM systems could becustomized to some specific market applications. Utilizing 3Dprogrammable logic or 3D gate array as has been described in someembodiments herein could be very effective. The need to reduce power toallow effective use of battery and also the light weight and small formfactor derived by highly integrating functions with low waste ofinterconnect and substrate could benefit from the redundancy and repairidea of the 3D monolithic technology as has been presented in some ofthe inventive embodiments herein. This unique technology could enabledisposable AEM devices that would be at a lower cost to produce and/orwould require lower power to operate and/or would require lower sizeand/or lighter to carry and combination of these features to form acompetitive or desirable AEM system.

3D ICs according to some embodiments of the invention could also enableelectronic and semiconductor devices with a much higher performance dueto the shorter interconnect as well as semiconductor devices with farmore complexity via multiple levels of logic and providing the abilityto repair or use redundancy. The achievable complexity of thesemiconductor devices according to some embodiments of the inventioncould far exceed what may be practical with the prior art technology.These advantages could lead to more powerful computer systems andimproved systems that have embedded computers.

It will also be appreciated by persons of ordinary skill in the art thatthe invention is not limited to what has been particularly shown anddescribed hereinabove. For example, drawings or illustrations may notshow n or p wells for clarity in illustration. Moreover, transistorchannels illustrated or discussed herein may include dopedsemiconductors, but may instead include undoped semiconductor material.Further, any transferred layer or donor substrate or wafer preparationillustrated or discussed herein may include one or more undoped regionsor layers of semiconductor material. Rather, the scope of the inventionincludes both combinations and sub-combinations of the various featuresdescribed herein above as well as modifications and variations whichwould occur to such skilled persons upon reading the foregoingdescription. Thus the invention is to be limited only by the appendedclaims

What is claimed is:
 1. A semiconductor memory, comprising: a firstmemory cell comprising a first transistor; a second memory cellcomprising a second transistor; a memory peripherals transistor, saidmemory peripherals transistor is atop said second transistor, whereinsaid second memory cell is above said first memory cell at a distance ofless than 200 nm, wherein said memory peripherals transistor is part ofa peripherals circuit controlling said memory, and wherein said secondmemory cell and said first memory cell have been processed following thesame lithography step and accordingly are self-aligned; and acopper-based connection layer disposed between said memory peripheralstransistor and said second memory cell.
 2. The semiconductor memoryaccording to claim 1, wherein said second transistor comprises a singlecrystal channel.
 3. The semiconductor memory according to claim 1,wherein said first transistor is a polysilicon transistor.
 4. Thesemiconductor memory according to claim 1, wherein said first transistoris a junction-less transistor.
 5. The semiconductor memory according toclaim 1, further comprising: an isolation layer disposed between saidmemory peripherals transistor and said first transistor.
 6. Thesemiconductor memory according to claim 1, wherein said memoryperipherals transistor comprises a single crystal channel.
 7. Thesemiconductor memory according to claim 1 further comprising: anisolation layer disposed between said memory peripherals transistor andsaid first transistor, wherein said isolation layer comprises a viahaving a radius of less than 400 nm.